V. Jacobson. IP headers for low-speed serial links. RFC 1144, Internet Engineering Task Force, February 1990.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....that avoid link layer error detection. In this paper, we analyze the influence of these problems on existing header compression algorithms. We also propose an adaptive header compression that gives better performance. 1 Previous Work Van Jacobson proposed a TCP IP header compression algorithm [5] for low speed links. TCP IP packets with compressed headers normally traverse a single link, with a compressor on one side and a decompressor on the other. The idea is to avoid transferring redundant information whenever possible. The decompressor should use information already known to recover ....

V. Jacobson. IP headers for low-speed serial links. RFC 1144, Internet Engineering Task Force, February 1990.

....errored datagrams which were consecutive in TCP sequence number space. In these cases, the datagram length is incorrect and both the checksum eld contents and the TCP payload of a bad packet match the next good packet. One possible cause is decompression of a link using Van Jacobson [4] header compression (VJ HC) where the decompresser dropped a packet (perhaps due to a link level CRC error) When the receiver decompresses the next correctlyreceived packet of that ow after the drop, the decompresser will reconstitute the packet header from deltas which do not include the ....

....a packet (perhaps due to a link level CRC error) When the receiver decompresses the next correctlyreceived packet of that ow after the drop, the decompresser will reconstitute the packet header from deltas which do not include the sequence number delta of the dropped packet. see section 4. 1 in [4]) The net e ect is that sequence numbers are cut o each packet and pasted on to the succeeding packet. This continues until an end to end TCP retransmissions kick in, whereupon the backward jump in sequencenumber space causes the VJ HC sender to send an uncompressed header, which nally ....

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Jacobson, V. Compressing TCP/IP headers for low-speed serial links. Internet RFC 1144, Information Sciencies Institute, Feb 1990.

....specific functions, such as paging and simple message passing, carried by people walking around. Even with general purpose machines, people are unlikely to perform complicated work that requires a lot of network connections on the fly. 3 Related Work 3. 1 TCP IP Header Compression Van Jacobson [13] proposed TCP IP header compression for lowspeed serial links, and Degermark et al. 8] provides both UDP IP and TCP IP header compression mechanisms over wireless networks. Their basic observation is that among a stream of consecutive packets, a large part of the header does not change very ....

....addresses and port numbers of the source and the destination. The size of the new header would be 12 bytes for IPv4, in comparison with 28 bytes of the UDP IP header and 40 bytes of the TCP IP header. We propose to further reduce the METP header size by employing the idea of header compression in [13] and [8] We add 4 bytes to the full METP header to include a connection ID,asequence number and a few flags. When a TCP connection is established, a full METP header is used and both the mobile host and the base station record a binding of the connection ID and the address information of this ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Network Working Group, Request for Comments 1144, February 1990.

....example, frame delivery delay on IS 95 is around 100ms. Reducing the datagram size again reduces FER at the expense of increasing header overhead. However, TCP overhead can be reduced to 3 5 bytes per datagram by employing header compression, a technique appropriate for low bandwidth serial links [15]. This optimization is feasible only for the TCP IP combination. Since CT systems use separate uplink and downlink channels, forward (data) and reverse (acknowledgment) traffic do not interfere as in the WLAN case. Rather surprisingly then, TCP offers potentially more bandwidth to the user than ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Internet Request For Comments, February 1990. RFC 1144.

....to specify which of the packet header s first 20 bytes have changed. Thinwire was relatively protocol neutral, but not optimized for common traffic. In early 1990, Van Jacobson proposed a TCP IP specific compression algorithm with many optimizations taking advantage of this protocol s intricacies [17]. Sending between 3 5 bytes of the 40byte header in the common case, VJ TCP header compression is efficient, and the most widely deployed header compression protocol. However, VJ compression only works with TCP IP packets, and derives many of its strengths from its rigid specification. Since ....

JACOBSON, V. Compressing TCP/IP Headers for Low-Speed Serial Links. Internet Engineering Task Force, Feb. 1990. RFC-1144.

....recent packet in the cache, for simplicity and performance. We strip packet headers including UDP TCP before searching for redundancy. This is not required for our analysis, but improves eciency, because headers are typically not repetitive. E ective schemes exist for compressing TCP headers [10]. As part of computing the number of redundant bytes, we charge each match region a small penalty that is intended to represent the space needed to encode it for transmission. We felt this penalty important because, if it were not present, we could ultimately detect 100 redundancy by observing ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links, February 1990. RFC 1144.

....related problems that affect transport layer performance in a mobile environment. We also describe some of the desirable features that a transport protocol specially developed for mobile hosts should have. 4.6. 1 Comparison with existing schemes Thinwire protocols [29] and TCP header compression [45] can help in improving the response time of interactive applications such as telnet on low speed links. However, these solutions do not deal with host mobility. Link layer retransmission (LLR) can be used on error prone wireless links to bring their error rate on par with that on the wired ....

....on behalf of the personal computer. TCP header compression was also suggested in the same proposal to reduce bandwidth requirements for single character transmission over the serial line. A more effective method for compressing TCP headers for low speed serial links was suggested by Van Jacobson [45] in 1990. As with thinwire protocols, this method also does not address the problems of lossy links and host mobility. A dynamic round trip time estimation scheme for the Rx RPC package used in AFS [34] was described in [6] to improve Rx performance over low speed SLIP links. 150 The proposed ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Request for Comments 1144, February 1990.

....end systems (i.e. a part of the installed software on all user computers) modifications are undesirable and difficult to manage. Therefore, alternative solutions to reduce ACK Congestion are needed to suit the characteristics of a DVB Network. 4. 1 TCP Header Compression TCP header compression [16] is widely used on modem links and may compress the TCP IP header. An ACK packet may be reduced by 70 over the return link. However, this compression ratio may not be sufficient to prevent ACK congestion when the asymmetric ratio is higher than 80. 4.2 ACK Suppression Another way to avoid ACK ....

....indicating potential data loss and triggering unnecessary retransmission of data. The TCP congestion control algorithms also trigger, reducing the transmission rate, and therefore throughput. Since ACKs arrive at the sender more quickly using header compression, the cwnd may grow more rapidly [16] (figure 3) However, 28 the compression ratio is not enough to eliminate ACK Congestion for a DVB network, which results in expiry of the TCP retransmission timer, and subsequent slow start. This results in only a small improvement in TCP throughput (figure 4) Unmodified (A) Number of ....

V. Jacobson, 'Compressing TCP/IP Headers for Low-Speed Serial Links', IETF, RFC1144,Feb 1990.

....can change significantly on short time scales over some network paths. A possible area of future work is to assess the stationarity of RTTs in the network (much as has been done for routes, loss rate and throughput [ZPS00] We now turn our attention to the second goal of this section. RFC 1144 [Jac90] suggests 100 200 ms as the amount of time that users can perceive in regards to responses from networks. We note that figure 9 shows that nearly 75 of the connections in the P 0 dataset experience average RTT delays over 100 ms and nearly 40 of the RTTs observed exceed 200 ms. This ....

Van Jacobson. Compressing TCP/IP Headers For Low-Speed Serial Links, February 1990. RFC 1144.

....version control represent intermediate versions as deltas; SCCS starts with an original version and encodes subsequent ones with forward deltas, whereas RCS encodes previous versions as reverse deltas from their successors. Jacobson s technique for compressing IP and TCP headers over slow links [11] uses a clever, highly specialized form of delta encoding. In spite of this history, it appears to have taken several years before anyone thought of applying delta encoding to HTTP, perhaps because the development of HTTP caching has been somewhat haphazard. The first published suggestion for ....

Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 1144, Network Working Group, February, 1990.

.... detailed discussions of DCE and ASN.1, can be found in [BN84, Tan88, CS93, CDK94] On RPC performance, the classic reference is [SB89] Critiques of the RPC paradigm appear in [TR88, BR94] On the problem of inconsistent failure detection with RPC: BG95] Other relevant publications include [BCLF94, BCLF95, BD95, BKT90, BM90, BN84, Bro94, EBBV95, EKO95, GA91, HP94, Jac88, Jac90, MRTR90, Ras86, SB89, TL93]. A good reference to DCE is [DCE94] and to OLE 2 is [Bro94] Kerberos is discussed in [SNS88, BM90, Sch94] Kenneth P. Birman Building Secure and Reliable Network Applications 96 96 5. Streams In Section 1.2 we introduced the idea of a reliable communications channel, or stream, that could ....

....of recent work on optimizing streams protocols (particularly TCP) for high performance network hardware. An analysis of TCP costs, somewhat along the lines of the RPC cost Chapter 5: Streams 103 103 analysis in [SB89] can be found in [CJRS89] Work on performance optimization of TCP includes [Jac88, Jac90, Kay94, KP93]. A summary of other relevant papers can be found in [Com91, Ten90, BD95] Other papers included in the biliography of this text include [BMP94, Com91, CS93, CT87, DP93, EBBV95, FJML95, Jac88, Jac90, KC93, KP94, MRTR90, PHMA89, RAAB88a, RAAB88b, RST88, RST89, SDW92, Tan88, CDK94] Kenneth P. ....

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Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 114, Network Working Group, February 1990.

....can change significantly on short time scales over some network paths. A possible area of future work is to assess the stationarity of RTTs in the network (much as has been done for routes, loss rate and throughput [ZPS00] We now turn our attention to the second goal of this section. RFC 1144 [Jac90] suggests 100 200 ms as the amount of time that users can perceive in regards to responses from networks. We note that figure 9 shows that nearly 75 of the connections in the P 0 dataset experience RTT delays over 100 ms and nearly 40 of the RTTs observed exceed 200 ms. This indicates that ....

Van Jacobson. Compressing TCP/IP Headers For Low-Speed Serial Links, February 1990. RFC 1144.

....by Internet hosts result in suboptimal performance due to the large delay bandwidth product of the DBS network. Because the connectivity of the earth station to the Internet is limited by a 1. 5 Mbps T1 line, the bandwidth asymmetry is adequately overcome by techniques such as SLIP compression [13]. However, the long latency and the limited reverse channel bandwidth increase latency for Web like accesses; we show that techniques such as persistent connections and pipelined requests (e.g. 24] lead to significant performance improvements. The rest of this paper is organized as ....

....(ack clocking [12] With asymmetric bandwidth, the flow of acknowledgements over the slow reverse channel could throttle the flow of data packets. One way of alleviating this problem is to reduce the size of the acknowledgement packets using techniques such as SLIP header compression [13]. Another is to send TCP acknowledgements less frequently (e.g. 16] although care must be taken to ensure that the sender does not become very bursty as a result. This may be achieved by regulating the transmission of data at a consistent rate within the TCP congestion window, using the ratio ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links, February 1990. RFC 1144.

....recovery between TCP and RLP. In fact, we did not find any incidents of competing error recovery during bulk data transfers, as discussed in Section 6.4. All measurements that yielded a utilization of 95 percent or less suffered from the impact of RLP link resets when TCP IP header compression [12] was used. This is further explained in Section 6.3. Figure 6 also shows the throughput range that sock (see Section 4.1) achieved for measurements that yielded the same utilization. Taking protocol overhead into account, the throughput was consistently close to the bit rate of the channel. These ....

....both ends of wide area wireless links, which we believe will be the bottleneck in a future Internet. 6.3 The Impact of RLP Link Resets One of the key findings of our measurements and analysis is an understanding of the impact of RLP link resets (see Section 3.1. 1) when TCP IP header compression [12] is used to reduce the per segment overhead. As with other differential encoding schemes, header compression relies on the fact that the encoded deltas are not lost or reordered on the link between compressor and decompressor. Lost deltas will lead to false headers being generated at the ....

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Jacobson V., Compressing TCP/IP Headers for Low-Speed Serial Links, RFC 1144, February 1990.

....acknowledgements flowing in a direction opposite to data packets) causes the sender s round trip time estimate to be highly variable. This inflates TCP s retransmission timeout value, thereby impairing loss recovery. The following are our major results and conclusions: SLIP header compression [13] alleviates some of the performance problems due to bandwidth asymmetry, but does not completely eliminate all problems, especially those that arise in the presence of bidirectional traffic. Connections traversing packet radio networks suffer from large variations in round trip time caused by ....

....queue of packets and remove all redundant acks for the connection, taking care not to remove any acks that have data associated with them. A connection is uniquely identified by the 4 tuple port . In practice, packets on the PPP queue are often header compressed using the algorithm described in [13], which makes it hard to offset into the header and obtain the necessary fields. There are several alternative approaches to solving this problem: 1. Decompress the compressed packets in the queue each time a new ack arrives and compare fields. This requires maintaining extensive decompression ....

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V. Jacobson. Compressing TCP/IP Headers for LowSpeed Serial Links, February 1990. RFC 1144.

....as suggested in section 5 below) gab beefed up this section. Must add M TCP. 4.11 Header Compression Alternatives Because Long Thin Networks are bandwidth constrained, every byte that can be compressed out of over the air segments is worth compressing. Van Jacobson header compression [RFC1144] describes a Proposed Standard for TCP Header compression that is widely deployed. Mechanisms for TCP and IP header compression defined in [IPHC, IPHC PPP] provide the following benefits: Improve interactive response time Allow using small packets for bulk data with good line efficiency Allow ....

Jacobson, V., Compressing TCP/IP Headers for Low-Speed Serial Links, RFC 1144, February 1990.

....past. 2. It may be expensive to multiplex several data streams within a TCP session at a very fine granularity because of the overhead of the TCP IP header (usually 40 bytes or more) If this is really an issue, header compression techniques similar to those used for low speed dialup lines [52] could be used to reduce the overhead. 3. TCP session does not share any information across hosts. There are situation where this may be advantageous. For instance, two hosts on a LAN could benefit by sharing information about the network path to a common server. The SPAND system [97] points ....

....a slower rate than if there had been no queuing of acks. Another consequence is that the growth of the sender s window size slows down. This is part of the reason why the downstream throughput with a dialup upstream link running SLIP [95] is so low (Figure 9. 1) SLIP header compression (C SLIP) [52] reduces the sizes of acks and hence decreases k, thereby improving performance. For instance, consider bandwidths of 10 Mbps and 28.8 Kbps in the two directions, and a data packet size of 1 KB. With the TCP timestamp option enabled, the ack size is 52 bytes with SLIP and 18 bytes with C SLIP. So ....

V. Jacobson. Compressing TCP/IP Headers for Low-speed Serial Links. RFC-1144, Feb 1990.

....of the total link usage. Of course, there exist many slow speed links for instance voice band modems, and increasingly, wireless links. On these links, header size is an important issue. In fact, even the IP header, at 20 bytes, is too big for dial up links, and requires header compression [60]. Thus, we have situations where the largest (CLNP) of the three headers is no problem, and others where the smallest (small SIPP) is too big. Fortunately, there are mechanisms for reducing the negative impact of a large or deep header. Both of them have already been mentioned. If the problem is ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Request For Comments 1144, University of Southern California Information Sciences Institute, February 1990.

....129 TCP IP ACK Figure 8: Example Station Identification Packet The conversation continues on as per the usual TCP IP method. 9 Transporting Compressed IP Over DUAL PR CIP In the design of DUAL, we believed it was possible to use the TCP IP header compression scheme used in Compressed SLIP [Jacobson 90] This would reduce header overhead from 18 40 octets (AX.25, IP, TCP) to 5 5 bytes (DUAL, compressed TCP IP) We wished to use the header compression scheme in such a way that the compressed headers did not grow in size, and any alterations to the scheme were small. This has been accomplished. ....

....down. This section will give an overview about how we are going to implement DUAL, and will discuss some of the basic idea and problem behind the compression algorithm. This implementation will use and modifies an existing SLIP CSLIP implementation. For more information about SLIP and CSLIP see, Jacobson 90] and [Romkey 88] respectively. 13 11.1 Implementation Overview As shown in Figure 13b) the implementation will modify the existing SLIP CSLIP implementation, Serial Lines IP, which is commonly used for point to point serial connections running TCP IP. The modification is mainly around the ....

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V. Jacobson. Compressing TCP/IP headers for low-speed serial links, RFC 1144, February 1990.

....However, the workstations are also used as clients of other workstations. All of the machines were idle during the tests. The network options consisted of switched 10 Mbit s Ethernet, 2 Mbit s wireless AT T WaveLAN, and Serial Line IP with Van Jacobson TCP IP header compression (CSLIP) [57] over 19.2 Kbit s V.32terbo wired and 9.6 Kbit s ETC cellular dial up links 1 . To minimize the effects of network traffic on the experiments, the switched Ethernet hub was configured such that the server, the ThinkPad Ethernet adapter, and the WaveLAN base station were the only machines on the ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Internet RFC 1144, Feb. 1990.

....header encoding, compresses TCP IP headers through differential encoding. It takes advantage of the predictable changes between successive headers for the same TCP connection. Such an encoding scheme has been previously demonstrated to achieve a 10 to 1 compression ratio of TCP IP headers [15]. In our calculations, we assume the same compression ratio for 40 byte TCP IP headers but leave 28 byte UDP IP headers intact. Efficiency (percentage) Compression Technique 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 none Pad Stripping Cell Header Suppression Datagram Header ....

....is currently used in the Internet by hosts connected to low speed serial lines. Predictive differential encoding of TCP IP headers has been implemented with minor modifications to the Berkeley Software Distribution (BSD) Unix kernel. The nature of these modifications are documented in Reference [15]. They are also included in a Serial Line IP (SLIP) software distribution that has been used for several years throughout the Internet. The same techniques are applicable within an ATM network if each TCP connection maps to a separate virtual circuit in a connection oriented ATM network. However, ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Network Working Group Request for Comments 1144, February, 1990.

....workstation based gateways) so that our modification has minimal impact on them. For example, IP Secure datagrams should have no trouble getting through Internet gateways. The IP Secure does not modify upper layer headers, so even mechanisms which does peak through such as TCP header compression [9] will continue to work. At the time of this writing, an initial implementation of IP Secure is complete for the PC AT compatible machines running BSD 386, and we are working on the SunOS 4.1.3 with NET 2 network module. Simple performance evaluation using two Gateway2000 (i486DX2 at 66MHz) showed ....

Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 1144, February 1990.

....to be a TCP IP packet and also carry the useful TCP timestamp option, which allows for a more accurate estimate of a TCP connection s RTT. S.Y. Wang, H.T. Kung Use of TCP Decoupling in Improving TCP Performance over Wireless Networks 19 Using the TCP header compression algorithm proposed in [32] and the twice algorithm proposed in [23] on wireless links, one can greatly reduce the size of header packets (and thus their PERs) without the bad effects on TCP s performance caused by dropping a headercompressed packet [23] The TCP header compression mechanism can compress the TCP IP header ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, RFC 1144.

No context found.

V. Jacobson. IP headers for low-speed serial links. RFC 1144, Internet Engineering Task Force, February 1990.

No context found.

Jacobson, V. (1990c) Compressing TCP/IP Headers for Low-Speed Serial Links, IETF RFC 1144

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